Passing red sponges that now paint Aquarius, a Spanish hogfish bears a scar on its belly where a tiny transmitter was inserted. Inside the habitat a computer picks up the transmitter's signals, allowing aquanauts to track fish as they move into, around, and out of the study area. "We have to understand the movement patterns of different species to design marine reserves that protect them," says Les Kaufman. "There's a lot to learn, but already we've begun to think more like fish."